I was doing 3-4hr z2 rides on Sundays all last winter. The amount of TV (football) and movies i was able to demolish my way through was damn impressive. I found I needed to set a little timer on my garmin for 15min that just beeped as a reminder to stand for 10-15 pedal strokes just to give the undercarriage some relief.
I’ll tell you though, you will dial in your fit pretty damn quick doing those rides 